The present invention relates to a control device by which a rotor being examined for unbalance on a dynamic balancing machine is indexed to a desired angular position after the detection of unbalance.
Stop control devices of this kind have been proposed in various publications. For example, Japanese Patent Examined Publication No. 45-24274 describes an automatic positioning device wherein the motor of a dynamic balancing machine is controlled by pulse signals developed by a photocell and pulse signals caused by unbalance vibration. When the angular position of unbalance has been detected, the rotor is positioned in a definite angular position.
This apparatus requires a low-speed motor for use in stopping the rotor in a prescribed angular position in addition to a high-speed motor for use in measuring the unbalance of the rotor. The provision of these two motors makes it indispensable to provide a clutch, etc., which leads to a complication of the construction. In addition, when the rotor is to be stopped, a switchover from the high-speed motor to the low-speed motor must be made so that the rotor may be subjected to low-speed revolution. Consequently, it takes time for the rotor to be stopped in a prescribed angular position.
Japanese Patent Examined Publication No. 62-39890 also describes an automatic positioning device wherein the counting of angle signals is initiated by the trigger action of a revolution signal developed after the start of deceleration control of the rotor. When the prescribed number of angle signals has been counted, the driving motor is stopped so as to automatically position the rotor in a prescribed angular position.
In this particular apparatus, the counting of angle signals is initiated by the trigger action of a revolution signal developed after the start of the deceleration control of the rotor. However, it is difficult to correctly produce the revolution signal after the start of deceleration control of the rotor, because the rotor no longer revolves at a prescribed measurement speed. Consequently, errors in stop position often occur.
Japanese Patent Unexamined Publication No. 62-127638 also describes a method and an apparatus for positioning a rotor in a balancing machine. However, this reference only describes a technical proposal for the improvement of accuracy in positioning the rotor and does not discuss a technical method or construction for reducing the time interval from the instant the rotor ceases to revolve at a measurement speed until the instant the rotor stops.